data_receiver.pony.patch

diff --git a/lib/wallaroo/core/boundary/boundary.pony b/lib/wallaroo/core/boundary/boundary.pony
index 6c947cbd3..46778acfd 100644
--- a/lib/wallaroo/core/boundary/boundary.pony
+++ b/lib/wallaroo/core/boundary/boundary.pony
@@ -352,6 +352,9 @@ actor OutgoingBoundary is (Consumer & TCPActor)
 
   fun ref receive_ack(acked_seq_id: SeqId) =>
     ifdef debug then
+      if not (acked_seq_id > _lowest_queue_id) then
+        @printf[I32]("BUMMER: receive_ack: acked_seq_id %s _lowest_queue_id %s\n".cstring(), acked_seq_id.string().cstring(), _lowest_queue_id.string().cstring()) /////// SLF TODO NEW BUG, make new GH ticket?
+      end
       Invariant(acked_seq_id > _lowest_queue_id)
     end